1. Field of the Invention
The present invention relates to a communication system suitable for use in communication of control information between the camera and lens assemblies of, for example, an interchangeable-lens type camera system.
2. Description of the Related Art
In recent years, imaging systems such as camera systems and video camera systems have been remarkably developing, and various kinds of imaging systems which have a variety of functions and which allow interchangeable lens assemblies to be used with a camera assembly have been available.
In such an imaging system, a camera assembly such as a video camera assembly (hereinafter referred to simply as a xe2x80x9ccamera assemblyxe2x80x9d) obtains from an interchangeable lens assembly specific information indicative of various characteristics and control information relating to the interchangeable lens assembly. The camera assembly in turn transmits predetermined control information to the lens assembly on the basis of the specific information so as to provide various kinds of control such as auto-focus (AF), auto-exposure (AE) and auto-zoom (AZ).
Transmission of the above-described control information and characteristics information is commonly realized by the communication performed between the camera and lens assemblies.
As is known, such an interchangeable-lens type imaging system is constructed of camera and lens assemblies which functionally differ from each other, and its total function is determined by a combination of the functions of the camera assembly and those of the lens assembly.
FIGS. 1(a) and 1(b) are schematic views showing system arrangements each provided by a combination of camera and lens assemblies in a camera system of the above-described type. A case where either of camera assemblies A and B having different functions is, as shown in FIG. 1(a), combined with either of lens assemblies C and D having different functions will be considered below.
It is assumed, as shown in FIG. 1(b), that the camera assembly A is capable of controlling an AF block A-AF for providing an AF function, an AE block A-AE for providing an AE function, an AZ block A-AZ for providing an AZ function and that the camera assembly B is capable of controlling only an AE block B-AE for providing an AE function.
It is also assumed that the lens assembly C includes an AF block C-AF, an AE block C-AE and an AZ block C-AZ and can selectively perform their functions. Further, it is assumed that the lens assembly D includes an AF block D-AF and an AE block D-AE and can selectively perform their functions.
In a first combination in which the camera assembly A and the lens assembly C are connected to each other by a serial communication line DL, the AF, AE and AZ functions can be performed. In a second combination in which the camera assembly A and the lens assembly D are connected to each other by the serial communication line DL, the AF and AE functions can be performed. If the camera assembly B is applied to either of the first and second combinations, only the AE function can be performed.
To assure reliable compatibility with respect to lens assemblies having different functions, as can be seen from the examples shown in FIGS. 1(a) and 1(b), control information based on a common format and detection information indicative of the driven state of each element needs to be communicated between the camera assembly A or B and the lens assembly C or D over the communication line DL. To achieve such communication, an appropriate common format is needed.
It is, therefore, an object of the present invention to provide an interchangeable-lens type camera system in which it is possible to smoothly control a lens assembly.
It is another object of the present invention to provide a camera system capable of efficiently controlling each function of a lens assembly by communication with a camera assembly.
It is another object of the present invention to provide a camera system in which control information associated with each unit to be controlled in a lens assembly and detection information indicative of the driven state thereof can be readily independently communicated between camera and lens assemblies irrespective of the number or kinds of units to be controlled, whereby it is possible to completely assure compatibility with respect to various lens assemblies including different numbers of units to be controlled.
To achieve the above objects, in accordance with one aspect of the present invention, there is provided a camera system capable of controlling a plurality of units in a lens assembly on the basis of control information transmitted from a camera assembly. The camera system comprises camera-side control means disposed in the camera assembly for transmitting the control information to the lens assembly, and lens-side control means disposed in the lens assembly for receiving the control information transmitted from the camera assembly and controlling the aforesaid plurality of units to be controlled. Each of the units includes driving means and detecting means for detecting a displacement provided by the driving means. The camera-side control means is arranged to serially transmit the control information on each of the units to the lens-side control means as a block corresponding to each of the units to be controlled, while the lens-side control means is arranged to drive the driving means in each of the units on the basis of the control information and to serially transmit to the camera-side control means information on each of the units, which is outputted from the detecting means, as a block corresponding to each of the units to be controlled.
It is another object of the present invention to provide a camera system in which each function of a lens assembly is controlled from a camera assembly, each function of the lens assembly being realized by a unit which includes a part for providing a desired function, a driving system, and detecting means for detecting the operating state of the part. The camera assembly transmits control information on each of the units to the lens assembly by serial communication, whereby each of the units of the lens assembly can be separately controlled in accordance with the control function of the camera assembly and the function of the lens assembly combined therewith.
It is another object of the present invention to provide a camera system in which control information associated with each unit to be controlled in a lens assembly and detection information indicative of the driven state thereof can be readily independently communicated between camera and lens assemblies irrespective of the number or kinds of units to be controlled, whereby it is possible to completely assure compatibility with respect to various lens assemblies including different numbers of units to be controlled.
It is another object of the present invention to provide an interchangeable-lens type camera system which can reliably controlling an interchangeable lens assembly by smoothly performing an initial communication for initializing the camera system and a control communication for effecting communication of substantial control information.
It is another object of the present invention to provide a camera communication system which makes it possible to reduce the requisite processing time without unnecessarily increasing the number of communication words even in a camera system of the type in which the number of communication words for an initial communication between camera and lens assemblies differ from the number of communication words for a control communication between them.
It is another object of the present invention to provide a communication system in which the number of communication words is variable so that the number of communication words can be increased or decreased as required and which can realize the functions of camera and lens assemblies connected to the communication system by utilizing a minimum communication system and without increasing the cost of a microcomputer or the like even in a case where the number of communication words is changed depending on the kind of communication.
To achieve the above object, in accordance with another aspect of the present invention, there is provided a camera system which controls a function of a lens assembly on the basis of control information serially transmitted from a camera assembly. The camera system is provided with communication means which effects communication of the control information and which is capable of changing the number of communication words associated with the communication, and means for transmitting, if the number of communication words is changed, the changed number of communication words from the camera assembly to the lens assembly.
In accordance with another aspect of the present invention, there is provided a camera system which controls a function of a lens assembly on the basis of control information serially transmitted from a camera assembly, which camera system includes first means for serially transmitting words indicative of the control information, second means for changing the number of words indicative of the control information transmitted from the camera assembly, and third means for transmitting, if the number of words for the control information is changed, the changed number of words to the lens assembly.
In accordance with another aspect of the present invention, there is provided a camera assembly to which a lens assembly can be detachably attached and which comprises communication means for effecting serial communication of the control information required to control a function of the lens assembly, changing means for finding the number of functions to be controlled or the state of the lens assembly and changing the number of communication words for the communication means, and means for transmitting, if the number of communication words is changed, information indicative of the changed number of communication words to the lens assembly.
In accordance with another aspect of the present invention, there is provided a data communication system which comprises communication means for selectively setting, between a master side and a slave side, a first communication mode for finding the state of connection of the system, a function of the slave side, etc. and a second communication mode for controlling the function of the slave side; and means for transmitting to the slave side information on the number of words for a communication mode which is selected if a mode switching operation is performed between the first communication mode and the second communication mode in a case where the number of communication words in the first communication mode differs from the number of communication words in the second communication mode.
In accordance with another aspect of the present invention, there is provided a data communication system suitable for use in a camera system which controls a plurality of functions of a lens assembly on the basis of information on individual communication words serially transmitted from the camera assembly. The data communication system comprises communication means capable of selectively setting an initial communication mode for finding the state of connection between the camera assembly and the lens assembly and a target to be controlled in the lens assembly and a second communication mode for controlling the functions of the lens assembly on the basis of the number of words which differs from the number of words used in the initial communication mode; and means for transmitting to the lens assembly information on the number of words for a communication mode which is selected if a mode switching operation is performed between the first communication mode and the second communication mode.
It is another object of the present invention to provide a camera system in which various kinds of system control are effected by means of synchronous communication performed between a camera assembly and a lens assembly. The camera system is provided with a word length change command indicative of a word length to be used as an operand in the next communication cycle, as one kind of initial/control command to be transmitted from the camera assembly to the lens assembly. The camera system is arranged in such a manner that a communication master side communicates a change in a communication word length to a communication slave side by using the word length change command before the change in the communication word length. Accordingly, it is possible to prevent the occurrence of a synchronization failure on the communication slave side or an increase in the number of unnecessary processes.
It is another object of the present invention to provide a camera system in which by using a word length change command in the control communication provided between camera and lens assemblies, it is possible to achieve smooth communication without causing a malfunction of the system or without the need to consume unnecessary processing time even if the number of communication words, the mode of communication or the like is changed.
It is another object of the present invention to provide a camera system which makes it possible to achieve a system provided with optimum communication word lengths for various combinations having different functions without the need to increase the amount of processing on a camera side or a lens side or without the requirement of excessively high throughputs on the lens side, that is, without the risk of causing an increase in the cost of a lens-side processing unit such as a microcomputer.
It is another object of the present invention to provide an interchangeable lens system which is arranged to perform communication between a camera assembly and a lens assembly. In such an interchangeable lens system, if the lens assembly does not include a control device, communication data transmitted from the camera assembly is directly sent back to the same. In this arrangement, the communication between the camera assembly and the lens assembly can be accomplished to inform the camera assembly that the lens assembly does not include any target to be controlled, without the need to incorporate any microcomputer in the lens assembly. In consequence, it is possible to eliminate the problem that it has been necessary to provide a microcomputer in a lens assembly which does not include any target to be controlled or that a camera assembly continues to transmit data without being able to detect the presence or absence of a target to be controlled in the lens assembly. Accordingly, it is possible to achieve smooth and rapid control.
To achieve the above object, in accordance with another aspect of the present invention, there is provided an interchangeable lens system which comprises a camera assembly; a lens assembly which can be detachably attached to the camera assembly; communication means for providing communication of control information between the camera assembly and the lens assembly; driving means in the lens assembly being controlled from the camera assembly through the communication means; and reply means for sending the control information back to the camera assembly as reply information indicating that there is no target to be controlled, if the lens assembly does not include any driving means corresponding to the control information supplied from the camera assembly to the lens assembly.
In accordance with another aspect of the present invention, there is provided a lens assembly which can be detachably attached to a camera assembly, which comprises reply means for sending control information, supplied from the camera assembly, back to the camera assembly as reply information indicating that there is no driving means, if the lens assembly does not include any driving means corresponding to the control information.
In accordance with another aspect of the present invention, there is provided a camera assembly to which a lens assembly can be detachably attached, the camera assembly comprising communication means for transmitting to the lens assembly control information required to drive driving means in the lens assembly and for receiving reply information sent back from the lens assembly; and control means for omitting control associated with the driving means, if the communication means receives from the lens assembly reply information indicating that the lens assembly includes no driving means corresponding to the control information.
In accordance with another aspect of the present invention, there is provided a control system comprising a master-side unit; a slave-side unit which can be detachably attached to the master-side unit; communication means for providing communication of control information between the master-side unit and the slave-side unit; driving means in the slave-side unit being controlled from the master-side unit through the communication means; and reply means for sending communication data, supplied from the master-side unit, directly back to the master-side unit as reply information indicating that there is no target to be controlled, if the slave-side unit does not include any target to be controlled corresponding to the control information supplied from the master-side unit.
It is another object of the present invention to provide a lens driving apparatus in which, even if a variation occurs in the time required to compute each kind of control information such as AE control information, the correspondence between computational information and information to be transmitted can be kept constant with respect to a lens assembly to be controlled. Accordingly, it is possible to achieve highly reliable control which is free from malfunction such as the transmission of partially omitted information or double transmission of the same information and which does not confuse a control operation.
To achieve the above object, in accordance with another aspect of the present invention, there is provided a lens driving apparatus which comprises driving means for driving an optical system; photoelectric conversion means for converting into an electrical signal an image signal formed on its image-forming surface by the optical system; computation means for performing computations on the control information required to control the optical system; communication means for communicating information indicative of the result of the computations performed by the computation means to the driving means at a predetermined communication timing; and control means for controlling the communication means so that the communication means transmits to the driving means the information indicative of the result of the computations performed by the computation means in synchronization with a communication timing which follows the time of completion of the computations.
In accordance with another aspect of the present invention, there is provided a lens driving apparatus which comprises driving means for driving an optical system; photoelectric conversion means for converting into an electrical signal an image signal formed on its image-forming surface by the optical system; memory means for storing at least part of the output signal of the photoelectric conversion means; computation means for performing computations on the control information required to control the optical system, by using a digital signal stored in the memory means; communication means for communicating information indicative of a result of the computations performed by the computation means to the driving means in synchronization with a vertical synchronizing signal; and control means for controlling the communication means so that the communication means transmits to the driving means the information indicative of the result of the computations performed by the computation means in synchronization with a vertical synchronizing signal which follows the time of completion of the computations.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention, taken in conjunction with the accompanying drawings.